1. Field of the Invention
This invention relates generally to flexible linkages of the type employed in watchbands, and is concerned in particular with an improved method of forming and mounting top shells onto the links of such linkages.
2. Description of the Prior Art
The invention is particularly suited for, although not limited in use to, the mounting of molded plastic top shells onto the top links of metallic expansible watchband linkages. The conventional expansible watchband typically includes a row of top links overlying a row of bottom links. The top links have hollow box-like configurations with open ends. Each bottom link is connected to two adjacent top links by pairs of U-shaped staples. Springs housed in the links coact with the staples to yieldably contract the band. The top and bottom links as well as the staples and springs are typically fabricated as metal stampings. Top shells, also typically fabricated as metal stampings, are applied to the top links to impart the desired ornamental appearance to the finished product.
Because of their relatively thin-walled constructions, stamped metallic top shells contribute only minimally to the overall weight of the finished product. In some cases, this has led to expansible watchbands being compared unfavorably to more expensive non-expansible bands, which characteristically rely on thicker and heavier links, usually produced as castings or machined components.
During the assembly process, the stamped metallic top shells are conventionally batch loaded into vibrating hoppers, from which they are fed along tracks to a work station for application separately to individual top links of the expansible band. As a result of rubbing against one another in the vibrating hoppers, as well as against the guide surfaces of the feed tracks, the metallic top shells inevitably experience surface scratching. However, this is of little practical import because the top shells must in any event undergo expensive post assembly polishing to remove stretch marks which inevitably result from their origination as three dimensional stampings from flat sheet stock.
The stamped metallic top shells also require precise orientation and alignment preparatory to being applied separately to individual top links. The complexities involved in doing so on a mass production scale make it difficult and in most cases impractical to apply more than two top shell designs to a particular band.
Recent developments in expansible watchband technology have demonstrated the feasibility of substituting non-metallic top shells, in particular those molded of plastic materials such as LEXAN and the like, for the conventional stamped metallic top shells. From the designer's standpoint, all plastic top shells open new windows of opportunity, including the introduction of vibrant colors and heretofore unachievable shapes and contours. From the manufacturing standpoint, beneficial savings can be realized because the plastic top shells exit the molds without surface blemishes which require post assembly polishing.
An object of the present invention is to capitalize still further on the use of plastic top shells by providing an improved more cost effective method of forming and applying them to the top shells of expansible watchbands.
A companion objective of the present invention is the provision of an improved method of forming and applying top shells which is advantageously useful not only for non-metallic molded top shells, but also for metallic top shells produced as castings or stampings.
Still another objective of the present invention is the provision of a method of forming differently designed top shells and of applying them in any selected combination and on a mass production scale, thereby making it possible to achieve heretofore unattainable decorative motifs which vary along the length of the watchband.